Mathematics
OpenStudy (anonymous):

assume that variables can represent any real number (see coments)

OpenStudy (anonymous):

$\sqrt{(a+9)^2}=$

OpenStudy (binary3i):

=|a+9|

OpenStudy (anonymous):

Let (a+9)=x $\sqrt{x^2}=\left| x \right|$ i guess you might know the answer from here onwards.